1. Field of the Invention
The present invention relates to a boron-doped diamond thin film having superconductivity.
2. Description of the Related Art
Diamond has always been adored as a jewel. What are even more fascinating about diamond are its outstanding physical properties; it is the hardest material ever known in the world with the highest thermal conductivity of 22 W/cmK. Pure diamond is an electrical insulator. However, with boron doping, it becomes a p-type semiconductor, with boron acting as a charge acceptor. It is a promising material for electrical applications such as high frequency and high power devices owing to its high breakdown field (>10 MV/cm) and high carrier mobility.
On the other hand, a heavily boron-doped diamond shows metallic conduction and it has been in use as eletrodes in the field of electrochemistry. Its physical properties, however, have remained largely unexplored, particularly at low temperatures. Therefore, the recent news of superconductivity at 2.3K in heavily boron-doped diamond synthesized by high pressure sintering was received with considerable surprise (E. A. Ekimov et al. “Superconductivity in diamond”, Nature, vol. 428, pp. 542, Apr. 1, 2004). Opening up new possibilities for diamond-based electrical or electronic devices, a systematic investigation of these phenomena clearly needs to be achieved. However, the systematic investigation of these phenomena has not been conducted sufficiently yet.